Is it a mean prank or my own paranoia?

I started my new job this past Monday. The first week has gone well so far. Originally, I was told that I had to wear ties, but I haven't figured out if that's a prank they play on all the newbies. Hopefully not, since I just went out and bought $100 worth of silk in the shape of neckties. Both of my interviews were on Fridays and I was told they could dress down to business casual on Fridays. Then I was told that they got a reprieve from wearing ties in August due to the heat wave. I showed up on Monday for the first day of work wearing a tie and promptly noticed I was the only one. They said that the August reprieve was extended through September 30. We'll see. All I know is that I'm not investing in any more ties until I see someone else wearing one :)